1. Field of the Invention
The present invention relates generally to a method and apparatus for sterilizing medical instruments, such as proctoscopes, and the like. More specifically, the present invention relates to a method and apparatus which utilizes electric current to sterilize medical instruments, such as proctoscopes, that have elongated tubular structures with interior surfaces on which stubborn and/or hard to clean biofilms are apt to form.
2. State of the Prior Art
Modern medical instruments which are used for exploratory or interdiction/surgical purposes within the human body require sterilization and/or cleaning between uses. In the case of exploratory devices such as proctoscopes, which are used for early detection of colon cancer, for example, careful cleaning between uses is required. Current practice, however, does not involve complete sterilization of proctoscopes between uses. Instead, a so-called "alcohol" cleaning is used. The reason for this resides in the manner in which this type of device is constructed. That is to say, there is usually at least one small internal tube running the full length of the proctoscope, which renders it virtually impossible to get alcohol, for example, into contact with all of the interior surfaces of the tube(s), and thus effectively attempt to kill all of the bacteria.
The construction of the proctoscope further precludes the use of normal heat sterilization (e.g. autoclaving) inasmuch as important elements are made of a plastic which does not exhibit sufficient resistance to elevated temperatures. However, even if it were to be possible to autoclave the device, the time required for sterilization would render it virtually impossible for a physician to use the device more than once a day.
U.S. Pat. No. 5,462,644 issued to Woodson on Oct. 31, 1995, discloses a method of killing microorganisms which form a biofilm on the surfaces of medical articles or on tissue or implant surfaces in a living subject. This sterilization is achieved by applying an electric field to an electrically conductive medium (viz., electrolyte) in which the biofilm is immersed.
The electrically conductive medium here includes a biocide or is capable of generating a biocide in situ upon application of the electric field. One example of the Woodson technique involves immersing an instrument such as a catheter, for example, in a bath having electrodes arranged at either end. The solution in which the catheter is immersed contains a suitable electrolyte and further can contain a sterilant such as glutaraldehyde.
While the woodson arrangement is claimed to have met with some success in the area of efficient cold sterilization, in the instance the medical instrument takes the form of a proctoscope, the process has met with only limited success due to the internal passage structure which is inherent with this type of device.
U.S. Pat. No. 5,312,813 issued to Costerton et al. issued on May 17, 1994, discloses a biofilm reduction method, which also involves the production of an electric field across the surface containing the biofilm which is subject to sterilization.
Another example of this type of sterilization arrangement is illustrated in the PCT patent application publication no. WO 92/19286. However, this arrangement, like those mentioned above, has not been particularly successful when applied to the sterilization of devices such as proctoscopes, which have elongated, small diameter, internal passage structures.